1. Field of the Invention
The present invention relates to a setting tool for driving in fastening elements and including a piston guide, a drive piston displaceable in the piston guide between its initial position and its setting position in which the drive piston drives in a fastening element, and a device for returning the drive piston to its initial position after completion of a setting process.
2. Description of the Prior Art
Setting tools of the type described above can be operated with solid, gaseous, or liquid fuels or with compressed air. In combustion-operated setting tools, the setting or drive piston is driven by combustion gases. The setting piston drives a fastening element in a constructional component.
Germani Publication DE 197 55 730 A1 discloses a setting tool having a piston guide in which a drive piston is displaceable. The piston guide itself is also axially displaceable in the tool housing. After completion of a setting process, the drive piston returns to its initial position. In a first step, the drive piston is displaced in a direction opposite the setting direction by an elastic element that was preloaded during the setting process. A further displacement of the piston takes places in a second step during a new press-on process when the bolt guide is displaced in the direction opposite the setting direction relative to the piston guide, entraining the drive piston therewith.
During the return stroke, it can happen that the drive piston would not completely return into its initial position. This is a serious drawback, in particular when during the following setting process, e.g, a nail, a bolt, etc., having a greater length should be driven in a constructional component. Further, the elastic return element is subjected to wear and, therefore, the periods between maintenance are reduced. Still further, return of the piston by the press-process requires application of a greater press-on force by the tool user.
Accordingly, an object of the present invention is to provide a setting tool of the type described above in which the drawbacks of conventional setting tools, e.g., those of DE 197 55 730 A1, are eliminated.